(a) Field of the Invention
This invention relates to novel compounds classified in the field of organic chemistry as [(aryl)(indolyl)(arylsulfonyl)]methanes; [(heteryl)(indolyl)(arylsulfonyl)]methanes; [(alkyl)(indolyl)(arylsulfonyl)]methanes; [bis(indolyl)-bis(arylsulfonyl)]alkanes; [bis(aryl)(arylsulfonyl)]methanes; [(heteryl)(pyrrolyl)(arylsulfonyl)]meth anes; [(aryl)(pyrrolyl)(arylsulfonyl)methanes; and [(aryl)(heteryl)(arylsulfonyl)]methanes useful as color precursors, particularly in the art of carbonless dupblicating as, for example, in pressure-sensitive systems and in thermal marking systems; to processes for preparing said methanes and alkanes; and to pressure-sensitive duplicating systems and thermal marking systems.
(b) Description of the Prior Art
Several classes of organic compounds of widely diverse structural types are known to be useful as colorless precursors for carbonless duplicating systems. Among the more important classes, there may be named phenothiazines, for example, benzoyl leuco methylene blue; phthalides, for example, crystal violet lactone; fluorans, for example, 2'-anilino-6'-diethylaminofluoran and 2'-dibenzylamino-6'-diethylaminofluoran; arylsulfinate salts of Michler's Hydrol; and various other types of colorless precursors currently employed in commercially accepted carbonless copy systems. Typical of the many such systems taught in the prior art are those described in U.S. Pat. Nos. 2,712,507, 2,800,457, 3,041,289 and 4,000,087, which issued July 5, 1955, July 23, 1957, June 26, 1962 and Dec. 28, 1976, respectively. Many of the color formers in the prior art suffer one or more disadvantages such as low tinctorial strength, poor light stability, low resistance to sublimation, low susceptibility to copiability of the color-developed form in standard office copying machines, for example, a xerographic type of copier, and low solubility in common organic solvents, the latter disadvantage thus requiring the use of specialized and expensive solvents in order to obtain microencapsulated solutions of sufficient concentration for use in pressure-sensitive copying systems.
The following items to date appear to constitute the most relevant prior art with regard to the instant application.
Licari and Dougherty in the Journal of the American Chemical Society, 76, 4039 (1954) describe the preparation and physical properties of 3-indolemethyl phenyl sulfone and 3-indolemethyl p-toluenesulfone from gramine and the corresponding sulfinic acid or its salts. It is indicated that the compounds might have bacteriostatic or plant growth factor characteristics. Hellmann and Muller in Chemische Berichte, 98, 638 (1965) describe the preparation and physical characteristics of 3-benzolsulfonylmethylindol, 3-[p-toluolsulfonylmethyl]indol and 3-[p-chlorobenzolsulfonylmethyl]indol from the interaction of indole containing an active hydrogen, paraformaldehyde and a sulfinic acid sodium salt in a mixture of acetic acid and N,N-dimethylformamide. There is no indication of the utility of the compounds. We have now discovered that the class of compounds of the types described by Licari and Dougherty, and by Hellmann and Muller, are readily converted to colored substances on thermal exposure. This property makes them useful for incorporation into thermal marking systems such as are used in recording and in duplicating systems.
Treibs and Herrmann, in Hoppe-Seyler's Zeitschrift fuer Physiologische Chemie 299, 168-185 (1955) [Chemical Abstracts 50: 944i (1956)] describe the preparation and physical characteristics of (2-methyl-3-indolyl)(p-dimethylaminophenyl)methene perchlorate from the interaction of 2-methylindole and p-dimethylaminobenzaldehyde in perchloric acid. No indication of utility for the compounds is given in the abstract.
U.S. Pat. No. 3,995,088, issued Nov. 30, 1976, discloses in most pertinent part a series of normally colorless leuco methylene dyestuffs of the formula ##STR1## wherein Y represents an amino-substituted phenyl residue of the formula ##STR2## or an indolyl residue of the formula ##STR3## wherein R.sub.1 and R.sub.2, independently of the other represent hydrogen, alkyl with 1 to 12 carbon atoms, alkoxyalkyl with 2 to 8 carbon atoms, benzyl or phenyl, R.sub.3 is hydrogen, halogen, nitro, alkyl having 1 to 4 carbon atoms or alkoxy having 1 to 4 carbon atoms, X.sub.1 represents hydrogen, alkyl with 1 to 12 carbon atoms, alkenyl with at most 12 carbon atoms or benzyl, X.sub.2 represents hydrogen, alkyl with 1 to 12 carbon atoms or phenyl and the ring A is unsubstituted or substituted by cyano, nitro, halogen, alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 4 carbon atoms or acyl with 1 to 8 carbon atoms, and Z represents alkyl with 1 to 12 carbon atoms, alkenyl with at most 12 carbon atoms, aryl, aralkyl, an heterocyclic radical or the residue of an organic, particularly aliphatic or cycloaliphatic compound having a ketomethylene group. The compounds are claimed as being useful as color formers in pressure-sensitive copying paper.
U.S. Pat. No. 3,193,404, issued July 6, 1965, discloses in most pertinent part, a series of normally colorless associated dye salts derived from interaction of sulfinic acid and benzhydrols. The salts are stated to be useful as color formers in carbonless transfer sheets and are represented by the formula ##STR4## wherein R is dimethylamino, diethylamino or methoxy, R.sup.1 is dimethylamino or diethylamino and Y is a C.sub.1 to C.sub.12 aliphatic group, phenyl or substituted phenyl.
German Offenlegungschrift No. 2,243,322, published Mar. 21, 1974, discloses in most pertinent part, a process for the preparation of a series of compounds having the formula ##STR5## in which Z.sup.1, Z.sup.2, Z.sup.3 and Z.sup.4, independently of each other, signify hydrogen, if need be, substituted alkyl, cycloalkyl, aralkyl or aryl, and Z.sup.1 and Z.sup.2 and Z.sup.3 and Z.sup.4 together with the nitrogen represent a heterocycle or at times combined with one of the radicals at the ortho-position of the benzene ring produce a condensed heterocycle, and Z.sup.5 is hydrogen, a halogen, an alkyl or alkoxy and Z.sup.6 represents a hydrogen, halogen, alkyl or alkoxy and Z designates, if need be, a substituted aralkylamino, cycloalkylamino, arylamino, a radical bound via a heterocyclic nitrogen or arylsulfonyl. The compounds are said to be formed by the oxidation of a substituted diphenylmethane and subsequent reaction with a compound of the formula ZM wherein Z is as defined above and M is hydrogen, or a sodium, potassium or ammonium cation. The compounds are disclosed as being useful as reaction dyestuffs for carbonless copying procedures.
German Offenlegungschrift No. 2,208,611, which was published Sept. 6, 1973, discloses a process for the preparation of a series of compounds of the formula ##STR6## wherein R is methyl or ethyl and R.sup.1 is phenyl or naphthyl substituted by an alkyl, chloro, nitro or alkoxy which comprises the condensation of the appropriate leucauramine of the formula ##STR7## and a sulfinic acid of the formula R.sup.1 -SO.sub.2 H in an acidic medium.
Hinsberg, in Chemische Berichte, 50 468-473 (1917), describes the preparation and physical properties of phenyl[4,4'-bis(dimethylamino)benzhydryl]sulfone prepared by the reaction of 4,4'-bis(dimethylamino)benzhydrol with benzene sulfonic acid in dilute hydrochloric acid. There is no indication of utility given for the product.